(44(2):147-156)Yield Loss and Control of Spiralling Whitefly (Aleurodicus Dispersus Russell)

螺旋粉蝨持續為害聖誕紅35天時，為害率與為害度分別為98％及82％，持續48天時全株葉片枯萎而喪失觀賞價值。為害番石榴植株如連續達4個月時，為害葉率可達64％，果實產量損失為80％。卵經浸藥法比較藥效，以2.8％ Bifenthrin EC 2,000倍殺卵效果最佳。經田間8種藥劑試驗結果，以90％ Methomyl WP 1,800倍防治若蟲效果最佳。成蟲以藥液乾膜法測試，經處理後24小時以90％ Methomyl WP 1,800倍處理者存活率最低，各藥劑處理成蟲經48小時後大致死亡。低毒類物質試驗中，以50％ Neem oil 200倍混合Triton 3,000倍防治效果最佳。以水速12.5公升／分作噴水處理，每二天噴一次，連續進行一個月，對若蟲防治率可達78.5％，成蟲為86.4％。The infestation rate and degree of infestation were 98% and 82% when poinsettia was consecutively attacked by spiralling whiteflies for 35 days. And most of leaves were chlorosis, withered, covered with sooty mold and appeared premature dehiscence on day 48 which made them lost their commercial value. If whiteflies attack guava for consecutive 4 months, the leaf infestation rate reached 64% and caused 80% fruit yield loss. Various synthetic chemical and non-chemical insecticides were tested in this experiment to control spiralling whitefly. Results indicated that 2.8% Bifenthrinate EC 2,000X gave the best eggs control among eight insecticides tested. However, 90% Methomyl WP 1,800X was more effective for nymphs in the field trial. Significant higher adults mortality was shown when treated with 90% Methomyl WP at the first 24 hours in residual film test, however, all adults died after 48 hours no matter which insecticide was applied. In low toxic substance treatment, 50% Neem oil 200X mixed with Triton 3,000X gave the best control rate. Water spraying at the rate of 12.5 1/mm. and 2 days interval for consecutive 1 month was able to control 78.5% of nymphs and 86.4% of adults